United States. Army. Army, 1st

First Army was constituted as an inactive unit of the Regular Army on August 9, 1932, pursuant to OCS 20696, August 9, 1932. It was activated at Fort Jay, New York, September 11, 1933, as one of four field armies headquartered in the continental United States by authority of AG Letter 320.2 (Sept. 2, 1933) September 11, 1933, and it exercised command over the I, II, and III Corps Areas. Headquarters First Army served concurrently with the Eastern Defense Command from June 21, 1941 through September 10, 1943. It departed the United States October 12, 1943, and opened a command post at Bristol, England, on October 20, 1943. It was assigned for administration to First U.S. Army Group October 19, 1943 through August 1, 1944; and to Twelfth U.S. Army Group, August 1, 1944 through May 21, 1945.

Its headquarters directed the training of U.S. forces committed to the initial assault upon Continental Europe, under the general supervision of the First U.S. Army Group. It prepared studies on supply and equipment requirements for Headquarters, European Theater of Operations, U.S. Army (ETOUSA), and directed the U.S. Army's share in an orientation program to promote understanding between U.S. and British troops. Under the Twenty-first Army Group commander it prepared the U.S. portion of the "initial assault plan" for the invasion of Europe, and during the initial assault it participated in the Build-Up Control Organization, which consisted of British and American military and naval representatives at Portsmouth who supervised the flow of troops units across the Channel.

The First Army's forces participated in the initial assaults along the Normandy coast on June 6, 1944, the capture of Cherbourg, the Battle of Northern France, the Battle of the Rhineland and the crossing of the Rhine. It advanced as far as Grimma on the Mulde. Besides combat operations, Headquarters First Army directed civil affairs and military government activities successively from beachhead operations in France, through Belgium, Luxembourg, the Netherlands, and Germany, and finally in Czechoslovakia.

Late in May 1945 it returned to the United States. Headquarters relocated to Fort Jackson, South Carolina, June 6, 1945; to Fort Bragg, North Carolina, September 20, 1945; and on June 11, 1946, moved to Fort Jay, New York. where it assumed command of all U.S. Army activities and installations in New England, New York, New Jersey, and Delaware. During its active periods, it controlled training formations in the United States itself. On January 1, 1966, First Army and Second Army were merged and at the same time First Army moved its headquarters to Fort George G. Meade, Maryland. The emphasis of First Army changed in 1973 from dealing with active units to reserve unit training and preparation. It remained at Fort Meade until 1995 when it moved to Fort Gillem, Georgia.

As of 2007, First U.S. Army was responsible for the training and mobilization of all Army Reserve and National Guard units in the United States. It had sub commands, First Army, Division East, headquartered at Fort George G. Meade, Maryland, and First Army, Division West, headquartered at Fort Carson, Colorado. Division East oversaw First Army's responsibilities in all states east of the Mississippi River while Division West oversees units in all states west of the Mississippi River.